Ultrafast Ion Transport via Dielectric Nanocube Interface

Abstract Drastic enhancement in the high‐rate capability of lithium‐ion batteries to the level of supercapacitors while maintaining high energy density is required for next‐generation power sources. Incorporating dielectric BaTiO₃ (BTO)‐based nanocubes (NCs) into the active materials–electrolyte interface provides an ultrafast charge transfer pathway via the dielectric layer. The highly dispersed NC‐decorated LiCoO₂ (LCO) treated at the optimized temperature of 600 °C displays significantly enhanced high‐rate capability; the cell maintains 56.7 mAh g^‐1 at 50C (1C = 160 mA g^‐1), which compares with null capacity at the same rate for bare LCO. Comparing the NCs with conventional sol‐gel‐derived nanoparticles, the capacity retention at 10C (vs 0.1C) steadily increases with increasing active materials–dielectric–electrolyte triple‐phase interface (TPI) in the NC‐decorated case, whereas the capacity retention decreases markedly at similar TPI density in the sol‐gel case. In the sol‐gel case, the amount of Li ions accumulating at the TPI greatly exceeds the maximum amount of Li ions involved in electron exchange through the redox reaction within the charge/discharge time. In the NC case, most Li ions at the TPI participate effectively in the redox reaction, which results in fast charge transfer since the TPI sites are abundantly supplied with Li ions.